Lamp guard

ABSTRACT

A lamp guard for protecting the lamp bulbs of hand lamps, trouble lamps, stringlights and the like is disclosed, wherein two flexible annular enclosure members, having tapered sides and molded from a transparent or translucent material, such as a synthetic polymer, are locked together by interengaging threads on the two members, and prevented from pulling apart by an annular retainer. An annular groove on one member receives an annular rib on the other, thereby forming a &#39;&#39;&#39;&#39;tongue and groove&#39;&#39;&#39;&#39; type of connection, wherein threads on one face of the rib engage similar threads on the adjacent wall of the groove, and the depths of the threads are greater than the clearance between the rib and the internal walls of the groove, whereby when a compressive force is applied to a side of the guard in the area of the connection between the two enclosure members, which would tend to pull the members apart at a point substantially 90* from the point where the force is applied and crush the guard, the threads of the tongue and groove construction together with the annular retainer will hold them together and prevent crushing.

United States Patent [191 Trevithick 11] 3,917,941 [4 1 Nov. 4, 1975LAMP GUARD [75] Inventor:

[73] Assignee: Daniel Woodl ead,Inc., Northbrook,

Ill.

[22] Filed: Oct. 17, 1974 [21] Appl. No.: 515,697

Tony Trevithick, Gumee, lll.

Primary ExaminerJoseph F. Peters, Jr. Attorney, Agent, or Firm-Johnson,Dienner, Emrich & Wagner [57] ABSTRACT A lamp guard for protecting thelamp bulbs of hand lamps, trouble lamps, stringlights and the like isdisclosed, wherein two flexible annular enclosure members, havingtapered sides and molded from a transparent or translucent material,such as a synthetic polymer, are locked together by interengagingthreads on the two members, and prevented from pulling apart by anannular retainer. An annular groove on one member receives an annularrib on the other, thereby forming a tongue and groove type ofconnection, wherein threads on one face of the rib engage similarthreads on the adjacent Wall of the groove, and the depths of thethreads are greater than the clearance between the rib and the internalwalls of the groove, whereby when a compressive force is applied to aside of the guard in the area of the connection between the twoenclosure members, which would tend to pull the members apart at a pointsubstantially 90 from the point where the force is applied and crush theguard, the threads of the tongue and groove construction together withthe annular retainer will hold them together and prevent crushing.

7 Claims, 4 Drawing Figures US. Patent Nov. 4, 1975 3,917,941

LAMP swan BACKGROUND or THE INvENrIoN Lamp guards molded from atransparent or translucent, flexible and heat-resistant material havebeen known and used heretofore, such as shown, for example, in my US,Pat. No. 3,767,913. Examples of lamp guards, other than the wellknownwire cage type, heretofore known, and formed of a transparent ortranslucent flexible plastic material are disclosed in US. Pat. Nos.1,695,468; 2,236,940 and 3,609,348.

Such lamp guards of the prior art, however, were usually open at one endor otherwise were so constructed that they would be crushed relativelyeasily, if they were stepped on by a person or run over by a smallvehicle.

The present invention is designed to overcome this disadvantage, and toprovide a construction which is not only light weight, but extremelystrong and crushresistant.

BRIEF SUMMARY or THE INVENTION The invention is directed in general to anovel construction of lamp guard, formed of a transparent ortranslucent, heat-resistant material, such as a synthetic polymer, andwhich is flexible. One example of such suitable material would be nylonand another is presently marketed under the trademark Lexan.

More particularly, the invention is directed to a lamp guard, which iscomprised of two annular enclosure members, comprising a base and a caplocked together by a novel threaded tongue and groove joint, which hasbeen found to be resistant to crushing when a force is applied on a sidethereof.

At least one of the members, and preferably both of them, have outerends of a lesser diameter than that of the inner ends thereof. The innerend of one member has an axially extending annular groove with thefaceof one of the walls thereof being threaded. The inner end of theother member has an axially extending annular groove with the face ofoneof the walls thereof being threaded. The inner end of the other memberhas an axially extending annular rib or tongue received within saidgroove. One face of the annular rib is provided with threads whichengage the threads in the groove, and when the two parts are thus lockedtogether, there is formed a complete lamp guard which will resistcrushing. I

Because the inner ends of theenclosure members have a diameter largerthan the diameter of the outer ends thereof, the sides of those memberswill be tapered or cone-shaped, although it is to be understood that theannular walls of such enclosure members can also be curved in an axialdirection, if desired, rather than flat, without departing from thespirit of the invention, and the resulting resistance to crushing willstill be present.

With this generally tapered configuration, a force applied at one pointalong the periphery of the inner end of the larger diameter will causethat end to be pushed inwardly at the point where the pressure isapplied and to be forced outwardly at points 90 from where the pressureis applied. Thus, when the two enclosure members are merely heldtogether by means such as adhesives or interengaging threads alone, theoutward movement thereof 90 away from where the pressure is applied willtend to pull the members apart, and suffi- 2 cient pressure will, infact, result in a pulling apart and crushing of the members.

By providing an outer annular retaining wall or skirt, integral with oneof the members, and spaced outwardly from the wall of the member, andforming the outer wall of the groove within which the annular rib on theother member is received, the members cannot be pulled apart in thatarea from where the pressure is applied, and, therefore, cannot becrushed. In fact, such construction makes the threads hold even tighterand the tendency to pull apart increases the resistance to crushing.

If the two enclosure members were tubular, with straight sides and thesame diameter at both ends, there would be no tendency for the membersto pull apart 90 away from where the force is applied, and, therefore,the sides thereof would be merely flattened and crushed.

DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal sectional viewthrough the lamp guard, embodying the present invention;

FIG. 2 is an elevational view in perspective of the two enclosuremembers comprising the guard, separated and illustrating the shapeassumed by the inner ends thereof when a compressive force is applied tothe opposite sides thereof;

FIG. 3 shows in dot-dash lines the approximate shape of the inner end ofan enclosure member in plan view, when a compressive force is applied tothe opposite sides thereof; and illustrating the changes in radialdimensions which take place; and

FIG. 4 is a fragmentary, sectional view of the assembled parts of theguard, illustrating a portion of the structure of FIG. 1 on an enlargedscale.

DETAILED DESCRIPTION OF THE INVENTION Referring now particularly to thedrawing, the lamp guard in its completely assembled condition isindicated generally by the numeral 1. The guard is comprised of twoenclosure members, identified by the numerals 2 and 3, wherein themember 2 may be considered to be the base thereof and the member 3, thecap.

The outer end of the base 2 is indicated by the numeral 4, and isprovided with a neck portion 5, extending outwardly therefrom. This neckmay be provided with an internal annular rib, so that a hand lamp or thelike, shown in phantom by the numeral 7, may be releasably connectedthereto. This construction forms no part of the present invention, butmerely illustrates one manner in which a housing for the lamp bulbsocket (not shown) may be provided.

When the housing for the threaded socket, whether it be a hand lamp,stringlight or other type, is connected to the base enclosure member 2,a light bulb may be inserted into the socket, at which time the otherpart or cap 3 of the guard may be assembled therewith.

The outer end 8 of the cap member 3 is preferably provided with asnap-in rivet 9, with which the end 10 of a hook member (not shown) maybe assembled. This construction likewise is not a part of the presentinvention, but illustrates the manner in which-a hook may be attached tothe lamp guard, and have a universal type movement in both a pivotingand a swiveling manner.

The inner end of the base enclosure member 2 is indicated generally bythe numeral 11. This inner end is provided with an outer annular skirt12 which is spaced outwardly from the inner wall 13 of the member 2,

3 thereupon providing an axially extending annular groove.

One wall of the groove, and preferably the inner wall thereof, isprovided with threads 14.

The inner end of the cap enclosure member 3 is indicated generally bythe numeral 15. This end is provided with the annular rib 16, one faceof which is provided with the threads 17.

When the two enclosure members are to be assembled, the annular ribforms a tongue as it is inserted into the groove of the base enclosuremember 2, and the mating threads on the rib and within the groove areengaged to lock the two enclosure members together.

The inner end of the cap member 3 may also be provided with a radiallyextending annular ledge 18, adapted to abut the outermost annular edgeof the skirt member 12, and thereby form a a stop member to limit theinsertion of the tongue into the groove.

Suitable openings are provided in the two enclosure members to allowventilation, and to prevent heat build up when the lamp is being used.To this end, there is provided a plurality of circumferentially spaced,axially extending vent openings 19 in the base member 2, and similaropenings 20 are provided in the cap member 3.

Referring now to FIGS. 2 and 3, it will become evident that when acompressive force is applied to the sides of the assembled guard in thearea where the two members are locked together the flexible nature ofthe guard will allow the sides to be pushed inwardly in the area wherethe force is applied, as shown in FIG. 2, whereupon the normal diameterof the member will be made smaller, as indicated at a-a in FIG. 3. Thisdistortion of the inner ends of the members will cause the pointsapproximately 90 away from where the force is applied to push outwardly,so that the diameter of these inner ends will be increased, as may benoted at b-b in FIG. 3.

In this configuration of the parts, it is evident that those points atb-b will tend to pull apart. If the inner ends of the two members whichare connected together are not confined in some way, they will, in fact,pull apart, and the compressive force thereupon will crush the twomembers of the guard.

There will, of course, be some slight clearance between the annular rib16 and the adjacent faces of the annular groove, and it is thereforenecessary that the depth of the threads be greater than this clearance.With the skirt l2 acting to restrain separation of the threaded parts,the outward force at the points b-b will actually make the threads holdeven tighter and prevent the two members from pulling apart, thereuponpreventing them from being crushed, and thus the arrangement providesfor a much stronger assembly.

In actual practice, the depth of the threads will be approximatelyone-sixteenth-inch and the clearance provided is substantially0.0l4-inch.

The provision of the outer ends of the members having a lesser diameterthan the inner ends thereof, as described above, is a necessary featureof the invention, since it has been found that if the two members aretrue tubes with the same diameter throughout the length thereof, therewill be no resistance to crushing, even if they are locked together bythe threaded tongue and groove arrangement, described above. The generaltapered configuration of the enclosure members, whether the sides arestraight or curved, is the element which creates the tendency of themembers to pull apart at points 90 away from where the pressure isapplied. Since the members cannot pull apart for reasons above outlined,the assembled guard cannot be crushed. The greater the taper, thestronger the guard becomes. With straight sided tubular members having aconstant diameter, all forces, when pressure is applied thereto, will bein the same direction. The taper of the members provides an angle sothat the force applied breaks up into two forces at different angles,and, therein resides the basis for the resistance to crushing, as abovedescribed.

Changes may be made in the form, construction and arrangement of partsfrom those disclosed herein without in any way departing from the spiritof the invention or sacrificing any of the attendant advantages thereof,provided, however, that such changes fall within the scope of the claimsappended hereto.

I claim:

1. A lamp guard comprising,

a. a first enclosure member formed of a flexible material adapted tohave a lamp mounted therein, and having a circular inner end portion,

b. a second enclosure member also formed of a flexible material andhaving a circular inner end portion cooperating with said firstenclosure member to form the completed guard,

c. the outer end of at least one of said members having a smallerdiameter than the inner end thereof,

(1. an axially extending annular groove around one of said membersadjacent the inner end thereof having inner and outer walls,

e. an axially extending annular rib around the other of said membershaving inner and outer faces thereon and received within said annulargroove of said one member, and

f. means removably securing said members together includinginterengaging threads on a wall of said groove and on a face of saidrib.

2. A lamp guard, as defined in claim 1, wherein the threads in saidgroove are on the inner wall thereof and the threads on said rib are onthe inner face thereof.

3. A lamp guard, as defined in claim 1, wherein said enclosure membersare provided with a plurality of axially extending circumferentiallyspaced openings.

4. A lamp guard, as defined in claim 1, wherein the axial length of saidrib is substantially equal to the axial depth of said groove.

5. A lamp guard, as defined in claim 1, wherein the depth of saidinterengaging threads is greaterthan the clearance provided between thefaces of said rib and the walls of said groove, thereby to preventseparation of said members when pressure is applied to the guard causingflexing thereof in the area of said threads.

6. A lamp guard comprising,

a. a first annular and flexible enclosure member adapted to have a lampmounted therein, and having a circular inner end portion,

b. a second annular and flexible enclosure member also having a circularinner end portion cooperating with said first enclosure member to formthe completed guard,

c. both of said enclosure members having tapered surfaces with the innerends thereof having a greater diameter than the outer ends thereof,

d. an axially extending annular groove having inner and outer wallsaround one of said members adjacent the inner end thereof,

e. an axially extending annular rib around the other of said membershaving inner and outer faces thereon and received within said annulargroove of the depth of Said interengaging threads being greater than theclearance between the face of said 5314 One member, and rib and theadjacent wall of said groove.

f. interengaging threads on a wall of said groove and A p guard, asdefined in Claim 6, wherein Said f f t M b 5 annular groove is on saidfirst member, and said rib is a ace 0 sai n o remova ysecure sai mem erson Said Second member together,

1. A lamp guard comprising, a. a first enclosure member formed of aflexible material adapted to have a lamp mounted therein, and having acircular inner end portion, b. a second enclosure member also formed ofa flexible material and having a circular inner end portion cooperatingwith said first enclosure member to form the completed guard, c. theouter end of at least one of said members having a smaller diameter thanthe inner end thereof, d. an axially extending annular groove around oneof said members adjacent the inner end thereof having inner and outerwalls, e. an axially extending annular rib around the other of saidmembers having inner and outer faces thereon and received within saidannular groove of said one member, and f. means removably securing saidmembers together including interengaging threads on a wall of saidgroove and on a face of said rib.
 2. A lamp guard, as defined in claim1, wherein the threads in said groove are on the inner wall thereof andthe threads on said rib are on the inner face thereof.
 3. A lamp guard,as defined in claim 1, wherein said enclosure members are provided witha plurality of axially extending circumferentially spaced openings.
 4. Alamp guard, as defined in claim 1, wherein the axial length of said ribis substantially equal to the axial depth of said groove.
 5. A lampguard, as defined in claim 1, wherein the depth of said interengagingthreads is greater than the clearance provided between the faces of saidrib and the walls of said groove, thereby to prevent separation of saidmembers when pressure is applied to the guard causing flexing thereof inthe area of said threads.
 6. A lamp guard comprising, a. a first annularand flexible enclosure member adapted to have a lamp mounted therein,and having a circular inner end portion, b. a second annular andflexible enclosure member also having a circular inner end portioncooperating with said first enclosure member to form the completedguard, c. both of said enclosure members having tapered surfaces withthe inner ends thereof having a greater diameter than the outer endsthereof, d. an axially extending annular groove having inner and outerwalls around one of said members adjacent the inner end thereof, e. anaxially extending annular rib around the other of said members havinginner and outer faces thereon and received within said annular groove ofsaid one member, and f. interengaging threads on a wall of said grooveand a face of said rib to removably secure said members together, g. thedepth of said interengaging threads being greater than the clearancebetween the face of said rib and the adjacent wall of said groove.
 7. Alamp guard, as defined in claim 6, wherein said annular groove is onsaid first member, and said rib is on said second member.